Download Adult Skin Prick Testing

Nurses in Allergy
Group
Standard Operating Procedure
Adult Skin Prick Testing
Compiled by members of the BSACI Nurses in Allergy Committee
The following standard operating procedure outlines how to perform a skin prick test and
is applicable to all health care professionals undertaking this role.
Skin prick testing (SPT) is a method used to determine the presence of specific IgE.
SPT should only be interpreted in conjunction with a clinical history as a positive SPT
alone is not diagnostic of clinical disease (1,2). Depending on the allergen, approximately
half of positive tests occur in patients who are not allergic to that allergen. SPT should
be performed by an appropriately trained and competent healthcare worker who is also
trained in recognition and treatment of anaphylaxis (3).
Exclusions
SPT reactions are inhibited by antihistamines and may be inhibited by tricyclic
antidepressants, topical corticosteroids and UV light treatment. Therefore where
possible inhibitory medication should be stopped or alternative testing methods
considered (1,2). Short acting anti-histamines should be stopped for 72 hours prior to
testing
Cautions
Caution should be taken when considering SPT in pregnancy, for patients with unstable
asthma or those taking beta blockers and/or ACE inhibitors(1,2).
Equipment
 Selected allergens and positive and negative control solutions (stored at +2+8oC). Check expiry date and date opened (some manufacturers state that skin
test solutions should be used within 6 months of opening.) (4)
 And/or fresh foods to be used for testing
 Skin prick test recording sheet
 Pen
 Individual sterile skin prick testing lancets
 Sharps bin
 Tissues
 Skin test measure
 Timer / clock / watch
 Emergency equipment should be available to treat anaphylaxis, including
adrenaline 1:1000 (5)
Preparation
Verbal consent for the procedure should be obtained. The procedure should be
undertaken in accordance with local infection control policy using appropriate hand
hygiene measures. Select appropriate test site free from eczema / dermatitis, the
preferred site is the forearm but the back may also be used.
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PROCEDURE (1,2,3,6)
RATIONALE
Ensure test site is free from body
lotion and moisturisers
Body lotion / moisturiser can
cause allergen drops to run,
causing cross contamination.
Test site should be hygienically
clean but does not need to be not
be cleaned with alcohol or
antiseptic
Ensure patient is in a comfortable
position sitting or, if needle
phobic, lying down.
To ensure patient is relaxed
and able to remain still during
the test.
Rest arm on a level surface, using
pillow if necessary.
Mark the test sites approximately
2.5cm apart, using first letter of
allergen being tested. Avoid the
skin creases (elbow and wrist)
Begin with the negative control
and end with the positive control
To ensure any reactions do
not overlap so that accurate
measurements can be made.
Place one drop of each selected
allergen solution* next to relevant
marked site.
To ensure accurate
identification of the allergen
when results are read
To provide consistency, to
prevent cross contamination
from the histamine control
and for patient comfort
because the histamine
control reaction time is the
quickest.
*for prick to prick testing see
additional guidance below.
Using gentle pressure, push the
lancet through allergen solution
and into the surface layer of the
skin at a 90O angle.
To ensure that the allergen
penetrates the outer surface
of the skin.
To reduce risk of causing
bleeding.
To ensure a standardised
test
Discard lancet into sharps bin
To ensure safe disposal of
sharps
Repeat the procedure for each
allergen and the controls using a
new lancet each time
To prevent cross
contamination of the
allergens
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Remove surplus allergen by
blotting test sites with tissue
ensuring that there is no cross
contamination between test sites.
To remove excess allergen
solution and prevent cross
contamination of test sites.
Advise patients not to scratch the
test sites whilst waiting for the
results to develop
To allow for accurate reading
of results.
Advise patients to report promptly
any systemic adverse reaction
To ensure prompt treatment
of any adverse reaction
Results should be read 10-15
minutes after the test. Measure
the wheal diameter in mm. For
asymmetric wheals measure the
longest extent of the wheal in mm
and the extent 90o to the first
measurement (eg 3x3mm).
To ensure accurate
assessment of the reaction is
recorded.
An imprint of the result can also
be made by drawing round the
wheal in pen and taking a print
using skin tape which can then be
stuck onto the results sheet.
The flare may also be recorded.
Any pseudopodia should be noted
but not included in the
measurement of the wheal
A wheal diameter of 3mm larger
than the negative control is a
positive reaction
A wheal response to the negative
control indicates dermographism
Document the response to
the negative control.
Interpretation of other
positive results must allow for
subtraction of the negative
control. The need for further,
alternative testing should be
considered by the clinician
who has requested the test.
Absence of a wheal at the positive
control suggests that a topical or
oral medication with antihistaminic
properties may have been taken.
Repeat the positive control and if
still negative record as an invalid
test.
Document that the positive
control has not reacted.
Either repeat the skin tests
off anti-histamines /other
medication or the requesting
clinician can consider specific
IgE serology.
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Advise the patient that the wheals
will fade, usually within an hour.
To inform the patient
Topical 1% hydrocortisone, oral
anti-histamines or a cold
compress may be given to relieve
severe itch in line with a
prescription.
Record the outcome of the test
including;
 date of test
 patient name, date of birth
and hospital number
 skin prick (SPT) or prick to
prick (PPT) method
 wheal size in mm
 any recent antihistamine
medication with date/time
of last dose.
 name, designation and
signature of person
performing the SPT
To enhance patient comfort
and relieve severe itch
Ensure accurate
documentation.
*Prick-to-prick testing with fresh foods
The food used for testing fruit and vegetables should be fresh and not tinned or cooked
as these processes can alter allergenicity.
For fruit / vegetables push lancet into a fleshy and juicy/moist site of the food (through
skin if normally eaten) and place a small amount of the food substance onto the skin.
Then introduce the lancet into the surface layer of the skin at a 90 O angle through the
food.
For other foods place a small amount onto the skin, where practical, or crush/grind and
make a paste using sterile saline and place this on skin before pricking through it with
the lancet.
Interpreting the Skin Prick/ Prick to Prick Test
Ensure that the results are discussed with the patient by an appropriate clinician and,
when applicable, allergen avoidance advice is given. It is important to be aware of the
distinction between sensitisation (a positive test without clinical allergy) and allergy.
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References
1 The skin prick test – European Standards Clinical and Translational Allergy 3:3
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3565910/
2 Bousquet et al (2012) Practical guide to skin prick tests in allergy to
aeroallergens Allergy 67: 18-24
http://onlinelibrary.wiley.com/doi/10.1111/j.1398-9995.2011.02728.x/pdf
[accessed 16.01.2015]
3 Fitzsimons R et al (2014) Allergy Nurse Competency Document BSACI
http://www.bsaci.org/professionals/nurses-specialising-in-allergies [accessed
16.01.2015]
4 Summary of product characteristics Soluprick Timothy Grass ALK Abello
http://www.alkabello.com/UK/products/soluprickSQ/Lists/Soluprick%20SQ/Timothy%20Grass%20SmPC
.pdf [accessed 15.10.2015]
5 UK Resuscitation Council (2008) Emergency Treatment of Anaphylactic
Reactions https://www.resus.org.uk/search/?q=anaphylaxis
6 King et al (2010) Paediatric Skin Prick Testing SOP BSACI
http://www.bsaci.org/Guidelines/Skin_Prick_Testing.pdf [accessed 16.01.2015]
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